Where did I go wrong?

This was my first attempt in my new Masterbuilt electric smoker. Pork Butt was in the smoker by 7am. It was small, only 3.5 pounds. IT at 160, I wrapped it in foil. Seemed to reach it's plateau at 180, as it sat there for about 45 minutes. When the IT reached 204, I checked other areas and they were at 207. Took it out of the smoker, double wrapped it in foil and towels, then threw it in the cooler. 2 hours later, it is no where near ready to pull apart. It is now in the crock pot cooking. However, the chunks I did manage to break off it are mighty tasty. But what did I do wrong?